Several occupations require the individual to be exposed to extreme heat and/or flames. To avoid being injured while working in such conditions, these individuals typically wear protective garments constructed of special flame resistant materials designed to protect them from both heat and flame.
To cite an example, firefighters typically wear protective garments commonly referred to in the industry as turnout gear. Such turnout gear normally comprises various garments including, for instance, coveralls, trousers, and jackets. These garments usually include several layers of material including, for example, an outer shell that protects the wearer from flames, a moisture barrier that prevents the ingress of water into the garment, and a thermal barrier that insulates the wearer from extreme heat.
Turnout gear outer shells typically comprise woven fabrics formed of one or more types of flame resistant fibers. In that the outer shell must withstand flame, excessive heat, and abrasion, it must be constructed of a flame resistant material that is both strong and durable. The National Fire Protection Association (NFPA) provides guidelines as to the strength a fabric must have in order to be used in the construction of outer shells. According to NFPA 1971, 2000 edition, the fabric must exhibit a tensile strength of at least 140 pounds (lbs.) in the warp and filling directions, and a trapezoidal tear strength of at least 22 lbs. in the warp and filling directions. The NFPA provides detailed guidelines as to the manner in which testing is to be conducted to determine both tensile strength and tear strength.